I've been using the MoinMoin Wiki from Debian Testing for some time and this morning I found it was upgraded from 1.5.8 to 1.6.2, and unsurprisingly, my Wiki installation stopped working, very obviously some data migration may be necessary.

After wasted some time, I found a good article: Thomas Waldmann's AnotherWayToMigrateFrom1.5To1.6. I couldn't find a good official migration guide like this, which told you that you must run cache cleaning and data migration.